1. Field of the Invention
This invention relates to an image pickup apparatus, an image pickup method and an image pickup program for generating a whole panoramic image by gradually and sequentially shifting the image pickup direction and pasting a plurality of picked up images side by side as well as to a recording medium adapted to store such images.
2. Description of the Related Art
Electronic still cameras have been and being popularly used. They are designed to convert the rays of light that pass through the lens of the camera as the camera shoots the object to be imaged by means of a solid state imaging element such as CCD into video signals, record the video signals on a recording medium and, if required, reproduce the recorded video signals. Many electronic still cameras are provided with a monitor screen so that the user can display a selected one of the still images that have been picked up and recorded. However, known electronic still cameras can shoot only a narrow scenic range that is limited by the view angle of the lens of the camera. In other words, the electronic still cameras cannot shoot a wide scenic range beyond the view angle of the lens.
In view of the above-identified circumstances, camera systems for obtaining a panoramic image have been proposed in recent years. Such camera systems are classified into the multiple lens type adapted to shoot a wide scenic range at a time and the single lens type adapted to gradually shift the image pickup direction and serially and continuously pick up unit images.
While the multiple lens type camera system has an advantage that it can be handled like an ordinary camera to generate a panoramic whole image at a time, it has a drawback that the entire camera system is costly.
On the other hand, the single lens type camera system (see, inter alia, Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 11-46317) is less costly but indispensably requires an image processing technique of generating a single panoramic whole image by bonding the unit images that are serially and continuously picked up together with overlapping areas in such a way that the boundaries of the unit images are not noticeable. However, such overlapping areas can remarkably increase or decrease when the image pickup direction is manually shifted. In the worst case, such overlapping areas can be totally lost to make the attempt of acquiring a whole image a complete failure.
Additionally, since unit images that are picked up at different clock times are pasted together with the single lens type camera system, a displacement or some other discontinuity is caused along the boundary of continuously picked up two images when an object is moving there. Then, the whole image that is ultimately produced can end up as failure.
Techniques of mechanically shifting the image pickup direction by means of a turntable that is equipped with a motor to pick up unit images have been proposed (see, inter alia, Patent Document 2: Jpn. Pat. Appln. Laid-Open Publication No. 6-225202). With the related art, a camera is fitted to a turntable that is securely held on a tripod and the turntable is driven to rotate slowly by means of a motor in order to mechanically shift the image pickup direction and pick up unit images.
The image pickup direction of a camera system can be changed freely when the camera system is securely held on a tripod and the turntable to which the camera is fitted is driven to rotate by means of a high precision motor. However, the obtained unit images can be blurred as a result of shifting the image pickup direction particularly when the user wants to manually adjust the image pickup direction or when the motor does not revolve highly precisely. Then, it may not be possible to produce overlapping areas in the unit images for the purpose of preparing a panoramic whole image by pasting the picked up unit images to make the attempt of acquiring a whole image a complete failure. Therefore, it may be recommendable for such a camera system to be adjusted in advance to produce large overlapping areas.
Image pickup apparatus adapted to pick up a plurality of unit images for a wide scene by means of a single lens for the purpose of obtaining a panoramic whole image have been proposed. However, any of the known image pickup apparatus that have been proposed in the past cannot realize a functional feature of being capable of obtaining a high quality panoramic whole image, while maintaining the economic advantage of commercially available digital cameras.
For example, Patent Document 2 discloses a camera having a functional feature of picking up a panoramic whole image and a rotary adaptor to be attached to the imaging section of the camera. The rotary adaptor takes the role of operating as drive source for driving the imaging section of the camera to turn. However, it gives rise to a number of problems when it is actually operated.
The first problem is that the camera is designed without properly taking the balance of the mass of the camera into consideration. The adaptor of the known camera takes the role of driving the imaging section of the camera to turn and is mounted on the camera to turn the camera main body itself. While it is ideal to turn only the lens and the necessary part of the imaging sensor, the known camera is designed to turn the camera main body itself that carries heavy parts including a battery. As a result, costly components have to be used to bear the rotary motion of the motor. Additionally, when the camera main body is hand-held for shooting, the user of the camera feels it cumbersome to hold the camera because the part held by hand is lightweight and the rotary part of the camera is heavy to make the balance of the mass of the camera inappropriate.
The second problem is that the user cannot operate the buttons of the camera and see the image being displayed on the display screen of the camera with ease. More specifically, various buttons including the shutter button and a display section are arranged on the camera main body that is driven to turn. When the user operates any of the buttons of the camera while he or she is turning the imaging section of the camera, the obtained image can be blurred to make the shooting operation unsuccessful. While such blurs may be avoided by using a release, it is not a general practice to use a release for a commercially available digital camera.
Additionally, since the display section of the camera also turns with the rotary motion of the imaging section of the camera, the user is required to follow the turning motion of the display section in order to visually confirm the shooting operation. Such a motion on the part of the user is also cumbersome to the user.
Furthermore, it is also cumbersome for the user to carry around the rotary adaptor that is not used frequently and only required to use when taking a panoramic picture. The camera system will be far from being compact and easy to carry if the rotary adaptor is constantly fitted to the camera main body.
Thus, rotary adaptors that are designed to be used for taking panoramic images have not been popular at all.
Japanese Patent No. 3348285 (Patent Document 3) describes an apparatus comprising a turntable arranged on a fixed base so that a camera system may be rotated by 360° for taking a panoramic picture by means of the apparatus. The apparatus is designed exclusively for taking panoramic pictures. The apparatus also comprises a photo-coupler for connecting a camera and a downstream processing section when shooting a visual field of 360° in a serial and continuously shooting session and a rotary angle sensor for gauging the rotary angle of the turntable to consequently make the apparatus very bulky and complex.
However, if such an apparatus is fitted to a commercially available digital camera in order to provide the camera with a functional feature of being capable of obtaining a panoramic whole image, the cost will inevitably be prohibitive. Additionally, such a known apparatus is designed to be arranged on a tripod and connected to an external computer for use. Therefore, it adversely affects a commercially available digital camera in terms of portability if it is fitted to the camera. Thus, it is not realistic to provide an ordinary camera with such a large and bulky apparatus.